AC Condensor Unit Not Starting with Thermostat

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  #1  
Old 09-13-12, 12:37 PM
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AC Condensor Unit Not Starting with Thermostat

Hey Everyone, great site here, lots of helpful information. I may as well make my first post an intro and a question.

I have an Intercity Products Home AC unit, approximately 20 years old. We have been in the house over 3 years with no issues. We have obviously had record breaking heat this summer in the midwest, so the AC unit has had heavy use (it has now finally cooled down).

When I turned the thermostat to cool and to a temp below the ambient temp, I hear the click and the blower kicks on. However, the outside condensor unit does not turn on. Upon further inspection, it appeared that the contactor was not being pulled-in when the cooling cycle was turned on. So, I replaced the contactor but still no luck. I can manually push the contactor in and the AC unit turns on and produces cold air.

I dont think it is the capacitor since the unit runs properly when the contactor is depressed (or could it?). I am familiar with the capacitor, but there are 2 other "devices" that are interconnected from the capacitor. This includes a cyclindrical can and a small square black box (labeled Kickstart). Is this part of the timing relay? Sorry for my amateur description.


So any suggestions? I will post a photo later this evening when I get home.


Thanks
 
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  #2  
Old 09-13-12, 04:32 PM
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you need to verify 24VAC is coming in on the thermostat wires from the house. You may have a safety switch inside the unit that is keeping the contactor from closing. FIrst verify voltage to the unit on the 2 low voltage wires. From there we will need a model number of the unit to determine if any safety switches are in the circuit or if you can post a picture of the wiring schematic that would help also.
 
  #3  
Old 09-13-12, 09:12 PM
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Thanks for the help. Unfortunately I won't be able to check the voltage until Sunday, as I am leaving town. I'll check the voltage and post a pic then. Do I need to disconnect the wire nut connections to check the voltage coming in through the 2 lower voltage wires?
 
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Old 09-14-12, 03:06 AM
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Yes. That is where you need to check
 
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Old 09-15-12, 10:24 AM
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Alright...I checked the voltage between the 2 low voltage wires and there was no voltage. I have 4 wires coming into the outside unit:
Red-->240 power into bottom of contactor
Black-->240 power into bottom of contactor
Green-->Assuming ground wire connected to unit
Brown-->4 smaller wires within; white wire connects to blue wire that connects to right side of contactor; red wire connects to black wire that runs inside unit (assuming the compressor or fan); 2 other wires are unused.

I attached a picture of the setup...
 
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  #6  
Old 09-15-12, 10:34 AM
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I take back my earlier statement; the 0 voltage I measured earlier was measured with the blower off. When the blower is turned on, the voltage between the 2 low voltage wires is ~27V.
 
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Old 09-15-12, 10:40 AM
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sounds like White and Red in the 18/4 wire is used. You need to follow the black wire that Red is attached to. Show pictures of what the black wire goes to and anything beyond that.
 
  #8  
Old 09-15-12, 11:35 AM
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Woohoo! I followed the black wire that the low voltage red wire was connected to. It ran to a pressure switch with a manual reset. I hit the reset and success!

Thanks for your help. Im glad it was something so simple. I'm sure I made it a lot more difficult than it needed to be but I learned a few things along the way.

 
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